If corrected serum calcium is 2.55 to 2.62 mmol/l, the dose of calcitriol will be reduced to 0.25 mcg twice weekly. Serum calcium will be rechecked after 2 weeks (or more frequently if indicated). If corrected serum calcium remains < 2.55 mmol/l, the dose of calcitriol will be maintained for the rest of the study period. If corrected serum calcium remains > 2.62 mmol/l for two consecutive measurements despite reducing the dose of calcitriol, the study medication will be stopped and the subject will be discontinued from the study.